Loss of enamel and a deep black stain of the teeth in a 40-year-old diabetic patient are strongly suggested to be caused by the daily consumption of a cheap white wine and, possibly, by the chewing of cayenne. The wine proved to be rather acid, thereby promoting abrasion as a result of gnashing, and to contain a high concentration of tannin.
- Oral Surg Oral Med Oral Pathol 1987 Oct;64(4):427-31 -- An unusual case of black teeth. -- Schuurs AH, Abraham-Inpijn L, van Straalen JP, Sastrowijoto SH.

It was found that a single dose of Capsicum fruit could affect pharmacokinetic parameters of theophylline, while a repeated dose affected the metabolic pathway of xanthine oxidase.
- Eur J Drug Metab Pharmacokinet 1995 Jul-Sep;20(3):173-8 -- Theophylline pharmacokinetics and metabolism in rabbits following single and repeated administration of Capsicum fruit. -- Bouraoui A, Brazier JL, Zouaghi H, Rousseau M.

Use extreme caution around children when using cayenne and capsaicin products. Recommendations have been found on the internet to use cayenne as a deterrent to thumb sucking -- please do not follow those questionable instructions.